Oral formulation for paclitaxel

ABSTRACT

A pharmaceutical formulation is provided for delivering paclitaxel in vivo comprising: water and micelles comprising paclitaxel and a pharrnaceutically-acceptable, water-miscible solubilizer forming the micelles, the solubilizer selected from the group consisting of solubilizers having the general structures 
     
       
         R 1 COOR 2 , R 1 CONR 2 , and R 1 COR 2 , 
       
     
     wherein R 1  is a hydrophobic C 3 -C 50  alkane, alkene or alkyne and R 2  is a hydrophilic moiety. The solubilizer is selected such that it does not have a pKa less than about 6.

RELATIONSHIP TO COPENDING APPLICATIONS

This application is a Continuation of U.S. application Ser. No.09/427,153, filed Oct. 25, 1999, now U.S. Pat. No. 6,136,846 which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to compositions that may be used aspharmaceutical compositions, methods and kits, more particularly toimproved pharmaceutical compositions, methods and kits includingpaclitaxel and pharmaceutically-acceptable, water-miscible solubilizers.

DESCRIPTION OF RELATED ART

Paclitaxel is a unique diterpene anticancer compound derived from thebark of the Taxus brevifolia (Pacific yew) tree. A crude extract of thebark demonstrated antineoplastic activity in preclinical tumor screening30 years ago as part of the National Cancer Institute's (NCI's)large-scale screening program. The active component of the extract,paclitaxel, was isolated and described by M. C. Wani et al, Plantantitumor agents. VI: The isolation and structure of Paclitaxel. a novelantileukemic and antitumor agent from Taxus brevifolia, J. Am. Chem.Soc. 93:2325-2327 (1971). This document, and all others referred toherein, are incorporated by reference as if reproduced fully below.

In 1979, Schiff and coworkers rekindled interest in the development ofpaclitaxel by demonstrating its novel mechanism of action. Paclitaxelstabilizes the tubulin polymer and promotes microtubule assembly, ratherthan inducing microtubule disassembly like the antimicrotubule agentscoichicine, vincristine, and vinblastine. This stabilization results inthe inhibition of the normal dynamic reorganization of the microtubulenetwork. Encouraging response rates (complete and partial) have beenreported in single-agent phase II studies of paclitaxel in breastcancer, previously untreated non-small-cell lung cancer, head and neckcancer, and refractory ovarian cancer.

Unfortunately, paclitaxel is poorly soluble in water (less than 0.01mg/mL) and other common vehicles used for the parenteral administrationof drugs. Certain organic solvents, however, may at least partiallydissolve paclitaxel. However, when a water-miscible organic solventcontaining paclitaxel at near its saturation solubility is diluted withaqueous infusion fluid, the drug may precipitate.

Solubilization of compounds with surfactants allows for dilution ofsaturated or near-saturated formulations. Consequently, researchersformulated paclitaxel formulations using 50% Cremophor EU50% dehydratedalcohol (USP, United States Pharmacopoeia), diluted in NS normal salineor D5W (5% dextrose in water) to a final concentration of 5% CremophorEL and 5% dehydrated alcohol or less, for the intravenous administrationof the drug to humans in early clinical trials. (Cremophor EL; BadischeAnilin und Soda Fabrik AG [BASF], Ludwigshafen, Federal Republic ofGermany). Paclitaxel for injection concentrate is currently availablefrom Bristol-Myers Squibb Co. (New York, N.Y.) in 30-mg (5-mL)single-dose vials. Each milliliter of formulation contains approximately6 mg Paclitaxel, 527 mg of Cremophor EL, and 49.7% (vol/vol) dehydratedalcohol. This concentrated formulation must be further diluted with NS,D5W, D5NS (normal saline, 5% dextrose in water and 5% dextrose in normalsaline) or D5W-R (Ringer's solution with 5% dextrose in water) prior toadministration. It has been noted that the Cremophor/Ethanol formulationof paclitaxel precipitates upon dilution with infusion fluid, andfibrous precipitates formed in some compositions during storage forextended periods of time. Additional information regarding Cremophorformulations of paclitaxel may be found in Agharkar et al., U.S. Pat.No. 5,504,102.

An unexpectedly high incidence of serious hypersensitivity reactions wasnoted in phase I studies of the paclitaxel/Cremophor formulations. D. M.Essayan et al., Successful Parenteral Desensitization to Paclitaxel, J.Allergy and Clin. Immun. 97:42-46 (1996). Studies have shown that theCremophor EL vehicle induces histamine release and hypotension in dogswithin 10 minutes of administration.

In January 1985, the NCI sent a letter to all phase I investigatorsusing paclitaxel, directing them to increase the duration of paclitaxelinfusions and to pretreat all subjects with antihistamines (both H1 andH2 antagonists) and steroids. The incidence of hyper-sensitivityreactions subsequently decreased. Because the infusion duration wasincreased and pretreatment medications were added at the same time, itwas not possible to determine whether infusion rate or pretreatment wasthe important factor.

Further studies were carried out in which paclitaxel was administeredafter premedication with steroids (such as dexamethasone),antihistamines (such as diphenhydramine), and H2-antagonists (such ascimetidine or ranitidine), and the infusion time was extended to 24hours in an attempt to eliminate the most serious allergic reactions.See Einzig, et al., Phase II Trial of Taxol in Patients with MetastaticRenal Cell Carcinoma, Cancer Investigation, 9:133-136 (1991); A. B.Miller et al., Reporting Results of Cancer Treatment,Cancer 47:207-214(1981). Additional description of premedication techniques may be foundin Carretta et al., U.S. Pat. No. 5,670,537.

There are other disadvantages to using Cremophor formulations as well.Polyvinylchloride (PVC) infusion bags and intravenous administrationsets usually contain diethylhexylphthalate (DEHP) as a plasticizer tomaximize component flexibility. DEHP leaches to some extent into aqueousinfusion fluids and blood products that come in contact with PVCmaterials. Exposure of animals to chronic high doses (more than 100mg/kg) of DEHP has resulted in toxic effects including growthretardation, liver weight increase, liver damage, testicular atrophy,teratogenicity, and carcinogenicity. Cosolvents and surfactants mayincrease the amount of plasticizer leached. Waugh and colleaguesevaluated the quantities of DEHP extracted from PVC infusion devices bythe commercially available paclitaxel formulation. Substantialquantities of DEHP were extracted by all formulation concentrationstested. Therefore, there is a substantial health risk to patientsreceiving paclitaxel in the commercially available formulation usingconventional PVC-containing equipment.

There is therefore a need for improved formulations comprisingpaclitaxel, methods of treatment using these formulations and kitscomprising these formulations, to overcome the stability problems and toalleviate the clinical side effects of conventional paclitaxelformulations as noted above and as known to one of skill in the art.

SUMMARY OF THE INVENTION

The present invention provides new and improved formulations ofpaclitaxel, methods of manufacturing these formulations, kits containingthese formulations and methods of treating cancer patients using theseformulations. The new and improved formulations include pharmaceuticallyacceptable, water miscible solubilizers other than Cremorphor which arebelieved to have improved long term stability and reduced adverseeffects relative to existing formulations.

In the present invention, a composition for delivering paclitaxel invivo is provided, which comprises paclitaxel; a solvent; and apharmaceutically-acceptable, water-miscible solubilizer selected fromthe group consisting of solubilizers having the general structures:

R₁COOR₂, R₁CONR₂, and R₁COR₂,

wherein R₁ is a hydrophobic C₃-C₅₀ alkane, alkene or alkyne and R₂ is ahydrophilic moiety. The solubilizer is selected such that it does nothave a pKa less than about 6. Optionally, the solubilizer does not havea pKa less than about 7, more preferably not less than about 8. Bydesigning the solubilizer to not have any acidic hydrogens, potentialdestabilization of paclitaxel catalyzed by anionic moieties may bereduced. Upon the addition of water, the solubilizer forms micelleswithin which the paclitaxel is solubilized in the aqueous solution.

The solubilizer may preferably be an ester (R₁COOR₂) derived from alipophilic acid (R₁COOH) that has been esterified with a hydrophilicalcohol (R₂OH). Examples of the lipophilic acids (R₁COOH) include longchain carboxylic acids such as lauric acid, palmitic acid, stearic acid,oleic acid, linoleic acid, archidonic acid, and d-α-tocopheryl acidsuccinate. Examples of hydrophilic alcohols (R₂OH) include polyalcoholssuch as polyethylene glycols (PEG): PEG 300, 400, and 1000. In apreferred embodiment, the solubilizer is a water miscible vitamin Ederivative, and is most preferably d-α-tocopherol polyethylene glycolsuccinate (TPGS).

The solvent in the composition may be pharmaceutically acceptable, watermiscible organic solvent that can dissolve both paclitaxel and thesolubilizer. Examples of suitable solvents include alcohols such asethanol, propylene glycol and benzyl alcohol; polyalcohols such aspolyethylene glycol (PEG); and amides such as 2-pyrrolidone,N-methyl-pyrrolidone and N,N-dimethyl acetamide.

The concentration of paclitaxel in the composition may preferably rangefrom about 5-20 mg/g, more preferably from about 8-15 mg/g, and mostpreferably from about 10-13 mg/g.

The concentration of solubilzer in the composition may preferably rangefrom about 40-90% w/w, more preferably from 45-75% w/w and mostpreferably from 50-60% w/w.

The weight ratio of the solubilizer to the solvent may preferably bebetween about 90:10-40:50, more preferably between about 70:30-45:55,and most preferably about 50:50.

The weight ratio of paclitaxel to the solubilizer may preferably bebetween about 1:10-1:100, more preferably about 1:20-1:80, and mostpreferably about 1:30-1:70.

In a preferred embodiment, the composition further comprises anacidifying agent added to the composition in a proportion such that thecomposition has a resulting pH between about 3 and 5. The acidifyingagent may be an organic acid. Examples of organic acid include ascorbicacid, citric acid, tartaric acid, lactic acid, oxalic acid, formic acid,benzene sulphonic acid, benzoic acid, maleic acid, glutamic acid,succinic acid, aspartic acid, diatrizoic acid, and acetic acid. Theacidifying agent may also be an inorganic acid, such as hydrochloricacid, sulphuric acid, phosphoric acid, and nitric acid.

Optionally, the solubilizer does not have a hydrogen with a pKa lessthan about 7, more preferably not less than about 8. By designing thesolubilizer to not have any acidic hydrogens, potential destabilizationof paclitaxel catalyzed by anionic moieties may be reduced.

The composition may be diluted into aqueous solution by adding saline orother infusion fluid for parenteral administration or intravenousinjection.

The composition may optionally be incorporated into a pharmaceuticalcarrier suitable for oral administration. For example, the compositionmay be filled into a soft or hard gelatin capsule, or other oral dosageforms. In these oral formulations, polyethylene glycols such as PEG 300and PEG400 may preferably be used as the solvent for solubilizingpaclitaxel, and the concentration of the solvent may preferably be lessthan about 40% w/w in the finally formed semi-solid or solidcomposition. These oral formulations may be administered into a host inneed thereof, such as a cancer patient.

In another embodiment, a composition is provided which is made by theacts comprising: providing paclitaxel; and combining the paclitaxel witha pharmaceutically-acceptable, water-miscible solubilizer selected fromthe group consisting of solubilizers having the general structures:

R₁COOR₂, R₁CONR₂, and R₁COR₂,

wherein R₁ is a hydrophobic C₃-C₅₀ alkane, alkene or alkyne and R₂ is ahydrophilic moiety. The solubilizer is selected such that it does nothave a pKa less than about 6.

In the present invention, a pharmaceutical formulation for deliveringpaclitaxel in vivo is also provided, which comprises water; and micellescomprising paclitaxel and a pharmaceutically-acceptable, water-misciblesolubilizer forming the micelles, the solubilizer selected from thegroup consisting of solubilizers having the general structures:

R₁COOR₂, R₁CONR₂, and R₁COR₂,

wherein R₁ is a hydrophobic C₃-C₅₀ alkane, alkene or alkyne and R₂ is ahydrophilic moiety. The solubilizer is selected such that it does nothave a pKa less than about 6.

The solubilizer may preferably be an ester (R₁COOR₂) derived fromlipophilic acids (R₁COOH) that are esterified with a hydrophilic alcohol(R₂OH). Examples of the lipophilic acids R₁COOH include long chaincarboxylic acids such as lauric acid, palmitic acid, stearic acid, oleicacid, linoleic acid, archidonic acid, and d-α-tocopheryl acid succinate.Examples of hydrophilic alcohols (R₂OH) include polyalcohols such aspolyethylene glycols (PEG): PEG 300, 400, and 1000. In a preferredembodiment, the solubilizer is a water miscible vitamin E derivatives,and is most preferably d-α-tocopherol polyethylene glycol succinate(TPGS).

The solubilizer contained in both the composition and the pharmaceuticalformulation is an amphiphilic ester (R₁COOR₂), an amphiphilic amide(R₁CONR₂) or an amphiphilic ketone (R₁COR₂) which is capable of formingmicelle in aqueous solution. Hydrophobic tails (R₁) of the solubilizeraggregate with lipophilic paclitaxel while hydrophilic heads (R₂) of thesolubilizer self-associate in water. Paclitaxel is thus solubized byassociating with the hydrophobic tails of the micelles in aqueoussolution.

The weight ratio of paclitaxel to the solubilizer may preferably bebetween about 1:10-1:100, more preferably about 1:20-1:80, and mostpreferably about 1:30-1:70.

The pharmaceutical formulation or the composition may optionally furtherinclude an excipient added to the composition in an amount sufficient toenhance the stability of the composition. Examples of the excipientincludes, but are not limited to, cyclodextrin such as α-, β-, andγ-cyclodextrin and modified, amorphous cyclodextrin such ashydroxy-substituted α-, β-, and γ-cyclodextrin.

Another pharmaceutical formulation is also provided, which is made bythe acts comprising: providing a stock compostion comprising paclitaxel,a solvent and a pharmaceutically-acceptable, water-miscible solubilizerselected from the group consisting of solubilizers having the generalstructures:

R₁COOR₂, R₁CONR₂, and R₁COR₂,

wherein R₁ is a hydrophobic C₃-C₅₀ alkane, alkene or alkyne and R₂ is ahydrophilic moiety, the solubilizer being selected such that it does nothave a pKa less than about 6; and combining the composition with anaqueous solution, wherein, upon addition of the aqueous solution, thesolubilizer forms micelles within which the paclitaxel is solubilized inthe aqueous solution.

One of the advantages of the above-described pharmaceutical formulationsand compositions is the use of a non-ionic, amphiphilic solubilizer forpaclitaxel. Previously, destabilization of paclitaxel by freecarboxylate anion in formulations of Cremorphor occurred. The use of anester, an amide or a ketone reduces this destabilization. By stabilizingpaclitaxel in the composition, the storage shelf life for thecomposition can be prolonged, while the potency or pharmaceuticalactivity of the pharmaceutical formulation can be enhanced.

Another advantage of the pharmaceutical formulation is that paclitaxelis entrapped within the micelles formed by the solubilizer. As a result,light-induced damage to paclitaxel may be reduced during the period ofinfusion.

A further advantage of the pharmaceutical formulation is that theaqueous solution contains paclitaxel-carrying micelles which remainphysically and chemically stable. The formulation can be administeredintravascularly without undue toxicity from undissolved drug orprecipitates of the solubilizer.

A kit containing a pharmaceutical formulation for delivering paclitaxelin vivo is also provided, the pharmaceutical formulation comprising:water and micelles comprising paclitaxel and apharmaceutically-acceptable, water-miscible solubilizer forming themicelles, the solubilizer having the general structures:

R₁COOR₂, R₁CONR₂, and R₁COR₂,

wherein R₁ is a hydrophobic C₃-C₅₀ alkane, alkene or alkyne and R₂ is ahydrophilic moiety, the solubilizer being selected such that it does nothave a pKa less than about 6.

A method for administering paclitaxel to a host in need thereof is alsoprovided, comprising: providing a pharmaceutical formulation comprising:water and micelles comprising paclitaxel and apharmaceutically-acceptable, water-miscible solubilizer forming themicelles, the solubilizer selected from the group consisting ofsolubilizers having the general structures:

R₁COOR₂, R₁CONR₂, and R₁COR₂,

wherein Ris a hydrophobic C₃-C₅₀ alkane, alkene or alkyne and R₂ is ahydrophilic moiety, the solubilizer being selected such that it does nothave a pKa less than about 6; and

administering the pharmaceutical formulation in a therapeuticallyeffective amount to a host in need thereof.

The method may be used for administering paclitaxel to patients. A widevariety of uses are known for paclitaxel including the treatment ofmalignant diseases such as cancer including, but not limited to, humanovarian cancer, breast cancer, malignant lymphoma, lung cancer,melanoma, and Kaposi's sarcoma. Other uses of paclitaxel may bedeveloped in the future. The present invention may also intended to beused in conjunction with these future uses of paclitaxel.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides new and improved formulations ofpaclitaxel, methods of manufacturing these formulations, kits containingthese formulations and methods of treating cancer patients using theseformulations. The new and improved formulations include pharmaceuticallyacceptable, water miscible solubilizers other than Cremorphor and arebelieved to have improved long term stability and reduced adverseeffects relative to existing formulations.

1. Compositions According To The Present Invention

In the present invention, compositions are provided which are used fordelivering paclitaxel in vivo. In one embodiment, the compositioncomprises paclitaxel, a solvent and a pharmaceutically-acceptable,water-miscible solubilizer selected from the group consisting ofsolubilizers having the general structures:

R₁COOR₂, R₁CONR₂ and R₁COR₂,

wherein R₁ is a hydrophobic C₃-C₅₀ alkane, alkene or alkyne and R₂ is ahydrophilic moiety, the solubilizer being selected such that it does nothave a pKa less than about 6. Upon the addition of water, thesolubilizer forms micelles within which the paclitaxel is solubilized inthe aqueous solution.

The composition for paclitaxel is formulated based on a combination of anon-ionic, amphiphilic solubilizer that forms micelles to solubilizepaclitaxel in an aqueous solution and a solvent that can dissolvepaclitaxel and disperse the solubilizer in the composition to form ahomogenous composition.

A pharmaceutical formulation can be formed from the composition byadding an aqueous solution such as water, saline or other infusionfluid. When an aqueous solution is added, hydrophobic tails of thesolubilizer aggregate with paclitaxel and entrap paclitaxel within amicelle, thereby solubilizing and stabilizing paclitaxel in theresultant pharmaceutical formulation.

In the composition, the solubilizer is an ester, an amide or a ketonewith a pKa less than about 6. As a result, the solubilizer isessentially non-ionic under pH 6 in an aqueous solution. Optionally, thesolubilizer may be selected such that the solubilizer does not have apKa less than about 7, more preferably not less than about 8.Maintaining non-ionicity of the solubilzer is believed to preventdestabilization of paclitaxel catalyzed by anions such as carboxylate.In contrast, the commercially available paclitaxel formulation with50:50 ethanol: Cremorphor contains carboxylate moieties which ionize andmay contribute to the decomposition of paclitaxel in the formulation.The present invention employs an amphiphilic ester as the solubilizer inthe composition, carboxylate anion-catalyzed decomposition of paclitaxelmay be minimized, thereby enhancing the stability and prolonging storageshelf-life of the drug.

The solubilizer R₁COOR₂ may preferably be an ester derived fromlipophilic acids (R₁COOH) that are esterified with hydrophilic alcohol(R₂OH). Examples of lipophilic acids (R₁COOH) include long chaincarboxylic acids such as lauric acid, palmitic acid, stearic acid, oleicacid, linoleic acid, arachidonic acid, and d-a-tocopheryl acidsuccinate. Examples of hydrophilic alcohols (R₂OH) include polyalcoholssuch as polyethylene glycols (PEG): PEG 300, 400, and 1000. In apreferred embodiment, the solubilizer is a water miscible vitamin Ederivative, and most preferably is d-α-tocopherol polyethylene glycolsuccinate (TPGS).

The solvent in the composition for delivering paclitaxel in vivo maypreferably be pharmaceutically acceptable, water miscible, nonaqueoussolvent that can dissolve both paclitaxel and the solubilizer. In thecontext of this invention, these solvents should be taken to includesolvents that are generally acceptable for pharmaceutical use,substantially water-miscible, and substantially non-aqueous. Preferably,these solvents do not cause phthalate plasticizes to leach when thesolvents are used with medical equipment whose tubing contains phthalateplasticizers. Preferred examples of the pharmaceutically-acceptable,water-miscible, non-aqueous solvents that may be used in this inventioninclude, but are not limited to, N-methyl pyrrolidone (NMP); propyleneglycol; polyethylene glycol (e.g. PEG300, PEG400, etc.); ethyl acetate;dimethyl sulfoxide; dimethyl acetamide; benzyl alcohol; 2-pyrrolidone;benzyl benzoate; C₂₋₆ alkanols; 2-ethoxyethanol; alkyl esters such as2-ethoxyethyl acetate, methyl acetate, ethyl acetate, ethylene glycoldiethyl ether, or ethylene glycol dimethyl ether; (s)-(−)-ethyl lactate;acetone; glycerol; alkyl ketones such as methylethyl ketone or dimethylsulfone; tetrahydrofuran; cyclic alkyl amides such as caprolactam;decylmethylsulfoxide; oleic acid; aromatic amines such asN,N-diethyl-m-toluamide; or 1-dodecylazacycloheptan-2-one.

Most preferred examples of pharmaceutically-acceptable, water-miscible,non-aqueous solvents include alcohols such as ethanol, propylene glycoland benzyl alcohol; polyalcohols such as polyethylene glycol (PEG 300,PEG 400, etc.); and amides such as 2-pyrrolidone, N-methyl-pyrrolidoneand N,N-dimethyl acetamide. Additionally, triacetin may also be used asa pharmaceutically-acceptable, water-miscible, non-aqueous solvent, aswell as functioning as a solubilizer in certain circumstances.

Pharmaceutical grade paclitaxel suitable for use in this invention maybe obtained from a variety of sources, including the National CancerInstitute (Bethesda, Md.). In the context of this invention, paclitaxelis intended to include paclitaxel proper, and paclitaxel derivatives,analogs, metabolites, and prodrugs thereof.

The composition may contain varying amounts of each of the paclitaxel,the pharmaceutically-acceptable, water-miscible solubilizer, solvent,and other ingredients. In a preferred embodiment, the inventivecompositions comprise paclitaxel in an amount ranging from about 5-20mg/g, more preferably from about 8-15 mg/g, and most preferably fromabout 10-13 mg/g.

In another preferred embodiment, the composition comprises a solubilizerin an amount ranging from about 40-90% w/w, more preferably from 45-75%w/w, and most preferably from 50-60% w/w.

In yet another preferred embodiment, the weight ratio of thesolubilizerto the solvent may be between about 90:10-40:50, morepreferably between about 70:30-45:55, and most preferably about 50:50.

In yet another preferred embodiment, the weight ratio of paclitaxel tothe solubilizer may be between about 1:10-1:100, more preferably about1:20-1:80, and most preferably about 1:30-1:70.

In yet another preferred embodiment, the composition further comprisesan acidifying agent added to the composition in a proportion such thatthe composition has a resulting pH between about 3 and 5. Adding anacidifying agent to the composition serves to further stabilize the bondto the carbonyl bond of the solubilizer and prevent carbonylanion-catalyzed decomposition of paclitaxel, if any.

Optionally, the solubilizer does not have a pKa less than about 7, morepreferably not less than about 8. By designing the solubilizer not toinclude a proton doner under physilogical conditions, potentialdestabilization of paclitaxel catalyzed by anionic moieties may bereduced.

The acidifying agent may be an organic acid including, but not limitedto, ascorbic acid, citric acid, tartaric acid, lactic acid, oxalic acid,formic acid, benzene sulphonic acid, benzoic acid, maleic acid, glutamicacid, succinic acid, aspartic acid, diatrizoic acid, and acetic acid.The acidifying agent may also be an inorganic acid, including, but notlimited to, hydrochloric acid, sulphuric acid, phosphoric acid, andnitric acid. An anhydrous organic acid may preferably be used in acomposition that may be further formulated for oral administration, suchas incorporation into soft or hard gelatin capsules, tablet or otheroral dosage forms.

The amount of acid added to the composition may be sufficient to adjustthe pH of the composition at preferably between about pH 3-6, morepreferably between about pH 3.5-5, and most preferably between about pH3-4.

The pharmaceutical formulation or the composition may optionally furtherinclude an excipient added to the composition in an amount sufficient toenhance the stability of the composition, maintain the product insolution, or prevent side effects associated with the administration ofthe inventive composition. Examples of excipients include but are notlimited to, cyclodextrin such as α-, β-, and γ-cyclodextrin andmodified, amorphous cyclodextrin such as hydroxy-substituted α-, β-, andγ-cyclodextrin. Cyclodextrins such as Encapsin® from JanssenPharmaceuticals may be used for this purpose.

The composition may be incorporated into a pharmaceutical carriersuitable for oral administration. In a preferred embodiment,polyethylene glycols, such as PEG 300 and 400, may be used as thesolvent for their capability of solubilizing paclitaxel and formingsemi-solid to solid compositions. In this embodiment, the concentrationof polyethylene glycol may preferably be less than about 40% w/w in thefinally formed composition. The composition may be filled into a soft orhard gelatin capsule, or another suitable oral dosage form withprotective or sustained release coatings and orally administered into ahost in need thereof, such as a cancer patient.

The types of protective or sustained release coating that may be usedinclude, but are not limited to, ethylcellulose,hydroxypropylmethylcellulose, hydroxypropylcellulose,hydroxyethylcellulose, and esters of methacrylic and ethacrylic acid(Eudragit RL, RS, and NE polymer products, Rohm Pharma, Darmstadt,Germany). The enteric protective materials or coatings may be, forexample, cellulose acetate pthalate, hydroxypropylmethylcellulose,ethylvinylacetate pthalate, polyvinylacetate pthalate and esters ofmethacrylic and ethacrylic acid (Eudragit S, Eudragit L and EudragitE30D, Rohm Pharma, Darmstadt, Ger.).

Alternatively, the composition may also be diluted into an aqueoussolution to form a pharmaceutical formulation by adding saline or otherinfusion fluid for parenteral administration or intravenous injection.The pharmaceutical formulation will be described in details below.

2. Pharmaceutical Formulations According to the Present Invention

In the present invention, pharmaceutical formulations for deliveringpaclitaxel in vivo are also provided, which comprise water and micellescomprising paclitaxel and a pharmaceutically-acceptable, water-misciblesolubilizer forming the micelles, the solubilizer selected from thegroup consisting of solubilizers having the general structures:

R₁COOR₂, R₁CONR₂, and R₁COR₂,

wherein R₁ is a hydrophobic C₃-C₅₀ alkane, alkene or alkyne and R₂ is ahydrophilic moiety, the solubilizer being selected such that it does nothave a pKa less than about 6.

The pharmaceutical formulation can be used for delivering paclitaxel invivo, preferably via parenteral administration. Parenteraladministration has been the preferred approach for paclitaxel as therapyfor systemic malignancies. Unfortunately, the currently availablepaclitaxel formulation which is based on a combination of ethanol andpolyoxyethylated castor oil (Cremorphor®, BASF, Germany) may precipitatewhen added to an infusion fluid. Cremorphor has been associated with aseries of clinical side effects necessitating extensive premedication todesensitize the side effects. By contrast, the formulation of thepresent invention contains a non-ionic ester solubilizer which formsmicelles in aqueous solution to solubilize paclitaxel without causingprecipitation, and delivers the drug into the body of a host in need.

Generally, micelles can solubilize otherwise insoluble organic materialby incorporating the organic material within their hydrophobic interior.The micelle in a pharmaceutical formulation is an association colloidthat displays regions of decreasing water solubility going from theoutside of the structure to the inside. Micelles are formed byamphiphilic molecules with both hydrophobic and hydrophilic moieties. Inthe present invention, the solubilizer is an amphiphilic ester with ahydrophobic tail (R₁) and a hydrophilic head (R₂). The hydrophobic tailof the solubilizer aggregates with lipophilic paclitaxel to form theinterior of the micelle while the hydrophilic head (R₂) of thesolubilizer self-associates with other hydrophilic heads and faces wateroutside of the micelle. Paclitaxel which is substantially insoluble inaqueous solution is thus solubilized by micelle formation.

The micelles may preferably be non-ionic, such that the head groupregion of a micelle resembles a concentrated aqueous solution of solute.A non-ionic head group, e.g. sugar or PEG, becomes hydrated by theaqueous solution and solubilizes the micelle. The non-ionic tail group,e.g. long hydrocarbon chain, aggregates with the lipophilic drug via vander Waals interactions, and occupies a range of areas by changing itsextended length, compressing or extending its hydrocarbon chain.

The solubilizer (R₁COOR₂) may preferably be an ester derived fromlipophilic acids (R₁COOH) that are esterified with hydrophilic alcohol(R₂OH). Examples of the lipophilic acids (R₁COOH) include long chaincarboxylic acids such as lauric acid, palmitic acid, stearic acid, oleicacid, linoleic acid, arachidonic acid, and d-α-tocopheryl acidsuccinate. Examples of hydrophilic alcohols (R₂OH) include polyalcoholssuch as polyethylene glycols (PEG): PEG 300, 400, and 1000. In apreferred embodiment, the solubilizer is a water miscible vitamin Ederivative, and most preferably is d-α-tocopherol polyethylene glycolsuccinate (TPGS).

TPGS is derived from vitamin E by esterification of the acid group ofd-α-tocopherol succinate with polyethylene glycol. In particular, thecommercially available TPGS 1000 esterified with PEG 1000 (EastmanChemical Company) is water soluble up to approximately 20 wt % andstable under heat sterilization conditions. In addition, the viscosityof TPGS 1000 appears to be constant and low at concentrations below 20wt %, a desirable property for a pharmaceutical formulation used inparenteral administration.

Other water miscible, amphiphilic solubilizer derived from d- ordl-α-tocopherol may also be used. For example, d- or dl-α-tocopherol maybe esterified by water soluble aliphatic dicarboxylic acid such asmalonic, succinic, glutaric, adipic, pimelic and maleic acid to form asalt, which is then further esterified with hydrophiles such as PEG toproduce water miscible, amphiphilic solubilizers.

In another preferred embodiment, the weight ratio of paclitaxel to thesolubilizer may be between about 1:10-1:100, more preferably about1:20-1:80, and most preferably about 1:30-1:70.

The pharmaceutical formulation can be used for delivering paclitaxel invivo, preferably via parenteral or intravenous administration. Since theaqueous formulation contains paclitaxel-carrying micelles which remainphysically and chemically stable, this formulation can be administeredintravascularly without undue toxicity from undissolved drug orprecipitates of the solubilizer and still maintains its pharmacologicalpotency. Further, in this formulation, paclitaxel is entrapped withinthe micelles formed by the solubilizer, thus light-induced damage topaclitaxel may be reduced during the period of infusion.

3. Manufacture of Pharmaceutical Compositions

The present invention also provides a method of manufacture ofpharmaceutical compositions. In one embodiment, a pharmaceuticalcomposition is made by the acts comprising: providing paclitaxel; andcombining the paclitaxel with a pharmaceutically-acceptable,water-miscible solvent and a pharmaceutically-acceptable, water-misciblesolubilizer selected from the group consisting of solubilizers havingthe general structures:

R₁COOR₂, R₁CONR₂, and R₁COR₂,

wherein R₁ is a hydrophobic C₃-C₅₀ alkane, alkene or alkyne and R₂ is ahydrophilic moiety, the solubilizer being selected such that it does nothave a pKa less than about 6.

In one variation of the embodiment, the pharmaceutical composition maybe prepared by dissolving paclitaxel in a small quantity of apharmaceutically-acceptable, water-miscible solvent with moderateagitation. The volume of the pharmaceutical composition is then made upwith the solubilizer dissolved in the solvent and other ingredients andmixed thoroughly.

In another variation of the embodiment, where the pharmaceuticalcomposition further comprises excipients, the excipients, such ashydroxypropyl cyclodextrin, may also be dissolved in an aliquot of thepharmaceutically-acceptable, water-miscible solvent. This aliquot maythen be mixed with a premixed solution of paclitaxel and solubilizer asdescribed above. The mixed aliquots are then mixed together, and theremaining volume is made up with the solvent, all under moderateagitation.

In yet another variation of the embodiment, where the pharmaceuticalcomposition further comprises an acidifying agent, the acidifying agent,may be added to the premixed solution of paclitaxel and solubilizer asdescribed above and mixed under moderate agitation. Examples of theacidifying agent include organic acids such as ascorbic acid, citricacid, tartaric acid, lactic acid, oxalic acid, formic acid, benzenesulphonic acid, benzoic acid, maleic acid, glutamic acid, succinic acid,aspartic acid, diatrizoic acid, and acetic acid, and inorganic acids,such as hydrochloric acid, sulphuric acid, phosphoric acid, and nitricacid. The amount of the acidifying agent may be sufficient to adjust thepH of the final formulation to a desired range after dilution of thepharmaceutical composition with infusion fluid, such as saline.

In another embodiment, a pharmaceutical composition is made by the actscomprising: providing a compostion comprising paclitaxel, a solvent anda pharmaceutically-acceptable, water-miscible solubilizer selected fromthe group consisting of solubilizers having the general structures:

R₁COOR₂, R₁CONR₂, and R₁COR₂,

wherein R₁ is a hydrophobic C₃-C₅₀ alkane, alkene or alkyne and R₂ is ahydrophilic moiety, the solubilizer being selected such that it does nothave a pKa less than about 6; and combining the composition with anaqueous solution, wherein, upon addition of the aqueous solution, thesolubilizer forms micelles within which the paclitaxel is solubilized inthe aqueous solution.

A kit containing a pharmaceutical formulation for delivering paclitaxelin vivo is also provided, the pharmaceutical formulation comprising:water and micelles comprising paclitaxel and apharmaceutically-acceptable, water-miscible solubilizer forming themicelles, the solubilizer selected from the group consisting ofsolubilizers having the general structures:

R₁COOR₂, R₁CONR₂, and R₁COR₂,

wherein R₁ is a hydrophobic C₃-C₅₀ alkane, alkene or alkyne and R₂ is ahydrophilic moiety, the solubilizer being selected such that it does nothave a pKa less than about 6.

4. Method of Administration In Vivo

A method for administering paclitaxel to a host in need thereof isprovided, comprising: providing a pharmaceutical formulation comprising:water and micelles comprising paclitaxel and apharmaceutically-acceptable, water-miscible solubilizer forming themicelles, the solubilizer selected from the group consisting ofsolubilizers having the general structures:

R₁COOR₂, R₁CONR₂ and R₁COR₂,

wherein R₁ is a hydrophobic C₃-C₅₀ alkane, alkene or alkyne and R₂ is ahydrophilic moiety, the solubilizer being selected such that it does nothave a pKa less than about 6; and

administering the pharmaceutical formulation in a therapeuticallyeffective amount to a host in need thereof.

The method may be used for administering paclitaxel parenterally topatients with malignant diseases such as cancer including, but notlimited to, human ovarian cancer, breast cancer, malignant lymphoma,lung cancer, melanoma, and Kaposi's sarcoma.

The pharmaceutical formulations according to the invention may beadministered in any medically suitable manner, preferably parenterallyor orally, more preferably parenterally, and still more preferablyintravenously. The pharmaceutical formulation may be prepared bydiluting the a composition as described in Section 1 with sterile water,normal saline, D5W, Ringer's solution or other equivalent infusionliquids.

Dilutions of the composition may preferably range from about 5:1 toabout 1:10 v/v of the composition to the diluting infusion liquids. Thedilutions may also be appropriately adjusted according to specifictreatment schemes adopted by clinicians. The ratio of v/v in thiscontext refers to the ratio of the volume of the composition beforedilution with the infusion fluids to the total volume of thepharmaceutical formulation following dilution with the infusion fluid.Additionally, the pharmaceutical may be administered in a bolus fashion.

When administering therapeutic agents such as paclitaxel, a highlystable formulation is desirable. Chemical stability of a formulationgenerally refers to the amount of chemical degradation of a particularagent in the formulation. Chemical stability of a pharmaceuticalformulation depends upon the amount of chemical degradation of theactive pharmaceutical ingredient in that preparation. Commonly,stability analysis of a pharmaceutical preparation, such as a liquidparenteral product, may be performed under accelerated temperatureconditions, such as in a 50° C. oven. For example, stability data for50° C. for one month can give assurance of stability for a minimum oftwo years at room temperature. The predictive nature of acceleratedstability studies at elevated temperatures is governed by the Arrheniusequation.

Developing formulations of acceptable chemical stability may beimportant, especially in cases where the composition comprises acytotoxic drug like the paclitaxel. Physicians will find products whichrequire determining the exact amount of paclitaxel present before usingthe products undesirable. Additionally, regulatory requirements mayspecify minimum stability requirements. Therefore, discovery ofvariables that impact stability is a useful step in development of newpharmaceutical formulations.

Acceptable stability is well understood by one of skill to mean chemicalstability that is sufficient for the material to be well accepted inclinical use, that definition being used herein. In a preferredembodiment, the chemical stability of paclitaxel in a 50° C. oven overfour weeks is greater than about 85%. In a more preferred embodiment,the chemical stability of paclitaxel in a 50° C. oven over four weeks isgreater than about 90%. In a still more preferred embodiment, thechemical stability of paclitaxel in a 50° C. oven over four weeks isgreater than about 93%. In a most preferred embodiment, the chemicalstability of paclitaxel in a 50° C. oven over four weeks is greater thanabout 96%.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the compositions, kits, andmethods of the present invention without departing from the spirit orscope of the invention. Thus, it is intended that the present inventioncover the modifications and variations of this invention provided theycome within the scope of the appended claims and their equivalents.Additionally, the following examples are appended for the purpose ofillustrating the claimed invention, and should not be construed so as tolimit the scope of the claimed invention.

EXAMPLES Example 1

Paclitaxel (10 mg) was dissolved in ethanol. Vitamin E TPGS (VTPGS, 700mg, Eastman Chemical Company) was melted at 50° C. and dissolvedseparately in ethanol in a ratio of 3:1, respectively. The paclitaxeland VTPGS solutions were mixed and ethanol was added to the solution toa final amount of 300 mg, resulting in a 7:3 weight ratio of VTPGS toethanol. Anhydrous ascorbic acid (5 mg) was then added to the mixture.The resultant stock solution (08-A) appears clear and yellow in color.The total volume of the stock solution was 25 mL.

Aliquots of the stock solution (08-A) was transferred into vials at 5muvial, and incubated at 4° C., 25° C., 40° C. and 50° C. respectivelyfor periods of time as listed in Tables 1A, 1B, 1C and 1D. Samples weretaken at one week or predetermined intervals and tested for chemicalstability. The stability testing was performed using an HPLC method. AnLC-F (penta-fluorophenyl bonded phase) 5 μm, 100 Å pore size, 4.6×250 mmcolumn was used. A UV detector set at 227 nm was used. The mobile phasewas made up of a 37:58:5 mixture of ACN:Water:MeOH (containing 1 mUL ofH₃PO₄). The flow rate was 1.2 muminute. The diluent used was acidicmethanol (MeOH containing 0.1% acetic acid). The sample concentrationwas 0.01 mg/mL. The injection volume was 20 μl. The retention time was14.5 minutes. The results are shown in Tables 1A, 1B, 1C and 1D.

One milliliter of the stock solution (08-A) was diluted to 5.0 mL with0.9% NaCl and observed for precipitation at room temperature for aperiod of at least 24 hr. The diluted solution had a pH of about 4. Theformulation did not show any signs of precipitation after over 24 hrs,

Example 2

Paclitaxel (10 mg) was dissolved in ethanol. Vitamin E TPGS (VTPGS, 600mg) was melted at 50° C. and dissolved separately in ethanol in a ratioof 3:1, respectively. The paclitaxel and VTPGS solutions were mixed andethanol was added to the solution to a final amount of 400 mg, resultingin a 6:4 weight ratio of VTPGS to ethanol. Anhydrous ascorbic acid (5mg) was then added to the mixture. The resultant stock solution (08-B)appears clear and yellow in color. The total volume of the stocksolution was 25 mL.

Aliquots of the stock solution (08-B) was transferred into vials at 5mL/vial, and incubated at 4° C., 25° C., 40° C. and 50° C. respectivelyfor periods of time as listed in Tables IA, 1B, 1C and 1D. Samples weretaken at one week or predetermined intervals and tested for chemicalstability of paclitaxel. The stability testing was performed using themethod outlined in Example 1. The results are shown in Tables 1A, 1B, 1Cand 1D.

One milliliter of the stock solution (08-B) was diluted to 5.0 mL with0.9% NaCl and observed for precipitation at room temperature for aperiod of at least 24 hr. The diluted solution had a pH of about 4. Theformulation did not show any signs of precipitation after over 24 hrs.or greater.

Example 3

Paclitaxel (10 mg) was dissolved in ethanol. Vitamin E TPGS (VTPGS, 500mg) was melted at 50° C. and dissolved separately in ethanol in a ratioof 3:1, respectively. The paclitaxel and VTPGS solutions were mixed andethanol was added to the solution to a final amount of 500 mg, resultingin a 5:5 weight ratio of VTPGS to ethanol.

Anhydrous ascorbic acid (5 mg) was then added to the mixture. Theresultant stock solution (08-C) appears clear and yellow in color. Thetotal volume of the stock solution was 25 mL.

Aliquots of the stock solution (08-C) was transferred into vials at 5mL/vial, and incubated at 4° C., 25° C., 40° C. and 50° C. respectivelyfor periods of time as listed in Tables 1A, 1 B, 1 C and 1 D. Sampleswere taken at one week intervals and tested for chemical stability ofpaclitaxel. The stability testing was performed using the methodoutlined in Example 1. The results are shown in Tables 1A, 1B, 1C and1D.

One milliliter of the stock solution (08-C) was diluted to 5.0 mL with0.9% NaCl and observed for precipitation at room temperature for aperiod of at least 24 hr. The diluted solution had a pH of about 4. Theformulation did not show any signs of precipitation after over 24 20hrs.

TABLE 1A Time (% Paclitaxel Remaining) (month at 4° C.) 08-A 08-B 08-C 0100 100 100 1 99 102 103 3 103 103 104

TABLE 1B Time (% Paclitaxel Remaining) (month at 25° C.) 08-A 08-B 08-C0 100 100 100 1 99 99 101 2 98 99 101 3 101 102 104

TABLE 1C Time (% Paclitaxel Remaining) (week at 40° C.) 08-A 08-B 08-C 0100 100 100 2 100 101 101 4 97 98 100 12 102 103 104

TABLE 1D Time (% Paclitaxel Remaining) (week at 50° C.) 08-A 08-B 08-C 0100 100 100 1 98 100 101 2 100 101 100 3 97 98 100 4 96 100 101

Example 4

Chemical and physical stability of the paclitaxel formulation followingdilution with normal saline was determined at certain time points afterthe dilution. Table 2 lists percentages of paclitaxel at indicatededtime points for a period of 24 hr. after 1:10 dilution of two paclitaxelformulations: paclitaxel at 10 mg/g in 50:50 ethanol: vitamin E TPGS,and paclitaxel at 12.5 mg/g in 50:50 ethanol: vitamin E TPGS.

TABLE 2 Paclitaxel (10.06 mg/g), Paclitaxel (12.44 mg/g), at 1:10dilution (1.01 mg/g) at 1:10 dilution (1.24 mg/g) Time (hr) % Paclitaxelremaining Time (hr) % Paclitaxel remaining 0 99.74 0 99.96 2 99.73 299.81 4 99.44 4 99.54 8 99.55 8 99.17 24 99.16 24 99.61

Table 3 lists observation of precipitation at indicated time pointsafter dilution of the paclitaxel formulation according the presentinvention with normal saline at indicated ratios. The paclitaxelformulation has paclitaxel at 12.5 mg/g in 50:50 ethanol: vitamin ETPGS.

TABLE 3 Dilution Precipitation after (hr) Ratio 0 24 32 47 71 1:5 NoneNone Yes Yes Yes 1:6 None None Yes Yes Yes 1:7 None None Yes Yes Yes 1:8None None None Yes Yes 1:9 None None None None Yes  1:10 None None NoneNone Yes

What is claimed is:
 1. A composition suitable for orally administeringpaclitaxel comprising: paclitaxel; and a pharmaceutically-acceptable,water-miscible solubilizer selected from the group consisting ofsolubilizers having the general structures R1COOR2, R1CONR2, and R₁COR2,wherein R1is a derivative of d-α-tocopherol and R2 is a hydrophilicmoiety.
 2. The composition according to claim 1, wherein the derivativeof d-α-tocopherol is esterified by polyethylene glycol.
 3. Thecomposition according to claim 1, wherein the solubilizer is esterifiedd-α-tocopheryl acid succinate.
 4. The composition according to claim 1,wherein the solubilizer is d-α-tocopherol polyethylene glycol succinate(TPGS).
 5. The composition according to claim 1, further comprising asolvent.
 6. The composition according to claim 5, wherein the solvent isan alcohol.
 7. The composition according to claim 5, wherein the solventis selected from the group consisting of ethanol, propylene glycol,benzyl alcohol, and polyethylene glycol (PEG).
 8. The compositionaccording to claim 5, wherein the solvent is PEG300 or PEG400.
 9. Thecomposition according to claim 8, wherein the concentration of PEG300 orPEG400 in the composition is less than 40% w/w.
 10. The compositionaccording to claim 1, wherein the concentration of solubilzer in thecomposition is between about 40% w/w and 90% w/w.
 11. The compositionaccording to claim 1, wherein the concentration of solubilzer in thecomposition is between about 45% w/w and 75% w/w.
 12. The compositionaccording to claim 1, wherein the concentration of the solubilzer in thecomposition is between about 50% w/w and 60% w/w.
 13. The compositionaccording to claim 5, wherein the weight ratio of the solubilizer to thesolvent is between about 90:10 and 60:40.
 14. The composition accordingto claim 5, wherein the weight ratio of the solubilizer to the solventis between about 80:20 and 70:30.
 15. The composition according to claim1, further comprising an acidifying agent.
 16. The composition accordingto claim 15, wherein the acidify agent is selected from the groupconsisting of ascorbic acid, citric acid, tartaric acid, lactic acid,oxalic acid, formic acid, benzene sulphonic acid, benzoic acid, maleicacid, glutamic acid, succinic acid, aspartic acid, diatrizoic acid,acetic acid, hydrochloric acid, sulphuric acid, phosphoric acid, andnitric acid.
 17. The composition according to claim 1, whereinpaclitaxel has a concentration in the composition between 0.1 and 20mg/g.
 18. The composition according to claim 1, wherein paclitaxel has aconcentration in the composition between 0.5 and 10 mg/g.
 19. Thecomposition according to claim 5, wherein the solvent is PEG300 orPEG400.
 20. The composition according to claim 1, wherein thecomposition is filled into a soft or hard gelatin capsule.
 21. Thecomposition according to claim 1, wherein the composition is coveredwith a protective or sustained release coating.
 22. The compositionaccording to claim 21, wherein the coating is selected from the groupconsisting of ethylcellulose, hydroxypropylmethylcellulose, celluloseacetate pthalate, hydroxypropylcellulose, ethylvinylacetate pthalate,hydroxyethylcellulose, and esters of methacrylic and ethacrylic acid.23. A method for orally administering paclitaxel to a host in needthereof comprising: providing a pharmaceutical composition comprisingpaclitaxel and a pharmaceutically-acceptable, water-miscible solubilizerselected from the group consisting of solubilizers having the generalstructures R1COOR2, R1CONR2, and R1COR2, wherein R1 is a derivative ofd-α-tocopherol and R2 is a hydrophilic moiety; and orally administeringthe pharmaceutical composition in a therapeutically effective amount tothe host in need thereof.